Defect-Controlled Photoresponse in GaOOH/Reduced Graphene Oxide Composites for Ultraviolet-C Photodetectors

GaOOH/reduced graphene oxide (rGO) composites are investigated for UVC photodetection with a defect-controlled photoresponse. The morphology and crystallinity of GaOOH grown on rGO are strongly influenced by the Ga(NO3)3 concentration. Excess precursor induces GaOOH aggregation, reducing the effective GaOOH/rGO interfacial area and generating trap states in GaOOH. These traps act as recombination centers that shorten the carrier lifetime and suppress the photocurrent. The optimized 10% Ga(NO3)3 device shows the best performance, achieving a responsivity of 63.82 mA/W and an external quantum efficiency of 31%, about four times higher than the 30% sample and ∼220 times higher than previously reported GaOOH-based photodetectors.